Oilfield operators demand a great quantity of information relating to the parameters and conditions encountered downhole. Such information typically includes characteristics of the earth formations traversed by the borehole, and data relating to the size and configuration of the borehole itself. The collection of information relating to conditions downhole, which commonly is referred to as “logging,” can be performed in real time during the drilling operation using logging while drilling (“LWD”) tools that are integrated into the drill string. For various reasons, these tools are preferably positioned near the bit where the drilling operation causes the downhole environment to be particularly hostile to electronic instrumentation and sensor operations. Tool failures, whether partial or complete, are all too common.
The data acquisition and control systems interface on the rig communicates with the LWD tools using one or more telemetry channels. The most commonly employed telemetry channels support data rates that are severely limited, forcing operators to choose among the available sensor measurements. Often, only the highest-priority measurements are communicated in “real-time” (in compressed form) and the rest are sent infrequently or stored for later retrieval, which may occur during pauses in the drilling process or perhaps be delayed until the drilling assembly is physically recovered from the borehole. Often, much of the data is discarded for lack of telemetry channel bandwidth and lack of adequate space in the downhole memory.
Thus many parameters of the downhole environment at any given time are unknown or poorly tracked. Impending tool failure detection and root cause diagnosis are issues that have not been adequately addressed, meaning that many downhole tool failures continue to be unexpected and “inexplicable”.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.